Welding behaviour of DUPLEX and SUPERDUPLEX …akademikpersonel.kocaeli.edu.tr/emelt/sci/emelt22.05.2013_05.04.06... · 50 Welding behaviour of DUPLEX and SUPERDUPLEX STAINLESS STEELS

48 1 Introduction

Duplex stainless steels (DSS), approximately with 50 % ferrite and 50 % austenite at their room temperature micro-structure, have been fi rst produced as wrought products in Sweden and as duplex castings in Finland in 1930. The ferritic-austenitic microstructure is achieved by maintain-ing a proper balance of ferrite-stabilizing and austenite-stabilizing elements in the alloy chemical composition and by providing a suitable solution heat treatment. Solution heat treatment of hot rolled plate between about 1 020 °C and 1 100 °C, followed by water quenching, produces a microstructure comprised of nearly equal proportions of ferrite and austenite. The duplex microstructure exhib-ited by these high-chromium alloys promotes a desirable combination of properties, including high toughness and strength levels, and corrosion resistance superior to those of the 3xx series austenitic stainless steels. Such property combinations have led to an increased application of these alloys by the chemical, petrochemical, marine industries, in power generation and in offshore applications. The supe-rior corrosion resistance, strength and/or combination of both properties due to their strict composition control and microstructural balance have provided these stainless grades to be used in many applications. [1-12].

In addition to chromium and molybdenum, nickel and nitro-gen are the other two major alloying elements. These alloy-ing elements enhance the resistance to pitting corrosion, crevice corrosion and chloride stress-corrosion cracking. Besides, dual phase microstructure they also provide high

room-temperature strength. Signifi cant improvements both in material design and weldability have been made leading DSS to range from the cost effi cient lean grades to the high alloyed superduplex grades for more demand-ing applications. The term of superduplex is usually asso-ciated with about 25 % Cr, ≥ 3.5 % Mo and > 0.2 % N providing an increased Pitting Resistance Equivalent Number (PRE

N) ≥ 40 [1-6]. Superduplex stainless steels belong to the duplex family and they have increased levels of Cr, Mo and N more than the standard duplex grades, resulting with a higher strength and improved corrosion resistance and resistance especially to stress corrosion cracking in H2S containing aggressive mediums [10-14].

The weldability of standard duplex stainless steel grades both with conventional arc welding processes [15-22] and with solid state processes [23, 24] has been reported by various researchers. Duplex stainless steels have good weldability similar to austenitic grades with a compara-ble alloying content. Although higher alloying content of superduplex weld metals compared to the duplex grades provides improved properties, are more sensitive to the variations in weld metal composition or welding parame-ters, that is why it is increasingly diffi cult to optimize weld-ing thermal cycles when the alloying content is increased. Superduplex stainless weld heat-affected zones are more stable resulting in a lower sensitivity for nitride precipi-tation [3]. Studies on weldability issues of SDSS grades have been conducted by various researchers as well [11, 14, 21, 25-28]. Given the increased use of duplex stain-less steels in as-welded conditions, a better understanding

AB

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1.4462 (UNS S31803) duplex stainless steel (DSS) and EN 1.4410 (UNS S32750) superduplex stain-less steel (SDSS) have been welded by fi bre laser welding and plasma arc welding (PAW) processes with-out fi ller metal. Impact toughness testing at various temperatures from 20 °C down to -60 °C was carried out. Microstructural examination included macro and microphotographs of the cross-sections, ferrite content measurements and hardness survey of the weld zones. Weld metal impact toughness results on the order of 100 J were obtained while values between 30 J and 60 J were measured respectively for plasma arc and laser welds of the duplex and superduplex grades even at -60 °C test temperature. Ferrite content of the welds varied generally in an acceptable range which affected the microstructure and the toughness proper-ties. Better toughness results of plasma arc welds of both duplex and superduplex material compared to the laser welds are attributed to the balanced microstructure of the weld metal having ferrite- austenite ratio close to 50:50 % obtained by controlled heat input.

IIW-Thesaurus keywords: Duplex stainless steels; Laser welding; Plasma welding.

Doc. IIW-2174, recommended for publication by Commission IX “Behaviour of Metals Subjected to Welding.”

Welding behaviour of DUPLEX and SUPERDUPLEXSTAINLESS STEELS using LASER and PLASMAARC WELDING processes

E. Taban and E. Kaluc

Welding behaviour of DUPLEX and SUPERDUPLEX STAINLESS STEELS using LASER and PLASMA ARC WELDING processes

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0708 2011 Vol. 55 WELDING IN THE WORLD Peer-reviewed SectionN°

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processes associated with very rapid cooling, increasing the risk of unbalanced microstructure [21, 14, 30].

To increase the productivity, there is an increasing interest in applying plasma arc welding (PAW) process in recent years. Concerning PAW of duplex grades, some studies have been realized by various researchers [13, 27, 29]. The fi rst use of fi bre lasers dates from the early 1960s, when low power lasers were used in optical amplifi ers. In 2000 the fi rst 100 W fi bre laser was produced for materi-als processing. Multi-kilowatt fi bre lasers have now been introduced for materials processing [35]. Since proper processes controlling the ferrite content of welds are very important [13-15, 18, 29, 30], present study is intended to explore the possibility of using plasma arc and laser weld-ing processes still obtaining an acceptable ferrite austen-ite ratio and desired properties for industrial applications. The welding conditions for autogenous welding without fi ller and with proper heat input is intended to be provided for the phase control. The weld properties obtained by means of plasma arc and fi bre laser welding processes were evaluated and compared for both duplex and super-duplex grades respectively.

In this study, impact toughness and microstructural prop-erties of plasma arc and fi bre laser welded 1.4462 duplex and 1.4410 superduplex stainless steel grades have been investigated while microstructure-property relation was evaluated. And the possibilities and limitations in using these processes for these grades in industrial fi elds with proper ferrite-austenite ratio have also been investigated.

2 Material and experimental

procedure

2.1 Material

EN 1.4462 (X2CrNiMo22.5.3, UNS S31803) duplex stainless steel and EN 1.4410 (X2CrNiMoN25.6.3, UNS S32750) superduplex stainless steel grades with a thickness of 6.5 mm have been used concerning pres-ent research. Chemical compositions of the base metals are given in Table 1. Data were obtained from chemical analysis by X-ray spectrometer and from the steel pro-ducer [36].

2.2 Welding

Plasma arc welding (PAW) of 1.4462 duplex and 1.4410 superduplex stainless steel grades have been realized in industrial conditions in keyhole mode without fi ller metal and by DCEN polarity. Straight plate edges perpendicular to the plate surface have been prepared while the weld pool was protected by a high purity Ar gas. One pass weld-ing was completed with a welding speed of 200 mm min-1.No preheat was applied while a heat input of approxi-mately 1.2 kJ/mm (0.6 PAW process effi ciency factor is taken into account) was used for both grades, which is

of those metallurgical factors that infl uence weldability should be gained. One of the main issues, concerning welding of duplex and superduplex grades, is mainly to obtain austenite amounts close to 50 % and to avoid the formation of deleterious intermetallic phases on cooling and reheating passes [10, 29]. The ferrite/austenite ratio depends on the energy input in welding, since it controls the cooling rate and ferrite/austenite transformation. Cooling time has strong effects on the impact toughness, so that the ferrite content and microhardness decreases with the increasing of cooling time. Very low heat inputs lead to high ferrite contents and intense chromium nitride precipitation, while high heat inputs and/or long exposure between 1 200 °C and 400 °C tend to produce precipita-tion of brittle phases like σ and χ. For these reasons, it is desirable to control welding parameters such that cooling is slow enough for adequate austenite formation, but also fast enough to prevent deleterious precipitation [4, 10, 14, 21, 30, 31].

Because the properties of duplex stainless steels and weld metals are dependent on the phase balance and can be affected by secondary phases, in order to obtain intended joint effi ciency and properties, the phase control in welding is important. And it is necessary to assure the continuity of duplex structure properties across the weld by controlling the phase balance both in the fusion zone and in the heat-affected zones (HAZ).The acceptable fer-rite content of the weld metal for practical applications is in the range of 30-70 % [3, 13, 14, 21, 29]. Higher ferrite content compared with base metal would reduce stress corrosion cracking resistance and the mechanical properties of the weldments. Ferrite content is in general a function of chemical composition and weld cooling rate which are related to the heat input during welding. For the common arc welding methods, using fi ller metals with increased nickel content and specifi ed minimum heat input is standard practice. In general, depending on the thickness and joint type, duplex stainless steels are recom-mended to be welded up to 2.0 kJ/mm heat input, while the upper limit of 1.5 kJ/mm is normally recommended in welding of superduplex stainless steels [10, 21].

The practical application of any steel on a larger scale depends on its weldability. Productivity is always a key issue in manufacturing and in principle productivity can be improved by increasing welding speed or by decreas-ing the number of weld beads. For mass production appli-cations, the advantages of plasma arc welding and laser beam welding processes (such as minimizing weld bead volume, increasing the welding speed and achieving a full automation), could be considered for cost effective design [21,31]. Although satisfactory literature was published on fundamental issues concerning welding and properties of arc welded joints, limited information is available on high productivity and high heat input density processes applied to DSS. A number of studies on beam welding of duplex stainless steels were reported such as electron beam welding [15, 32], laser welding [31, 33] and hybrid process [21, 34]. However, attention should be paid for autogenous processes and, in particular, for beam welding


50


5 mm-thick and 10 mm-wide, reduced to 8 mm by notch-ing and thus so-called ‘sub-sized’ test samples in accor-dance with TS EN 875 and TS EN 10045-1. Multiplying the results with a factor of two yields a good estimation for the equivalent toughness of a standard notch impact specimen. Impact toughness testing of over one hundred samples – three samples for each position, for each tem-perature, per weld – was carried out at 20 °C, 0 °C and at subzero temperatures such as -20 °C, -40 °C, and -60 °C. Since much welding technology associated with duplex stainless steels has been generated from offshore appli-cations, signifi cant emphasis is placed on the low tem-perature properties of the WM and HAZ [20], so impact testing was carried out at sub-zero temperatures as well.

3 Results and discussion

3.1 Microstructure

The microstructural examination on the specimens of all joints has been carried out using LOM and with x200 magnifi cation. The investigation of the welds has been performed from BM across HAZ to WM respectively. The macrographs are given in Figure 1 and microstructures of the related base metal and weld zones are shown in Figures 2 and 3 respectively for both PAW and laser welds of duplex and superduplex grades.

lower than the upper limit of the recommended range [10, 36, 37]. Fibre laser welding of both grades were accom-plished by a 4 kW fi bre laser equipment without fi ller metal with a welding speed of 1 270 mm/min. Butt welding with a high purity Ar purging gas was provided without preheat and in one pass with a heat input approximately about 0.2 kJ/mm, Table 2, [37].

2.3 Microstructural investigation

For metallographic evaluation, specimens were prepared, polished, and etched electrolytically in NaOH solution. Photomacro- and micrographs were obtained by light optical microscope (LOM) with 200× magnifi cation in the BM, WM, and HAZs. Ferrite content measurements in fer-rite % were done with a Fischer Ferritscope across BM and HAZ from both sides and WM of the cross-sections. To confi rm the data, also ferrite-austenite contents were measured by image analysis system. The Vickers micro-hardness was determined at a load of 1 kg from the face and root sides.

2.4 Impact toughness testing

Subsized notch impact test samples were extracted trans-verse to the weld. Notches were positioned at the weld metal centre (WM), including heat-affected zone (HAZ), and base metal (BM). It should be taken into account that toughness of the 6.5 mm-thick welds was measured on

Table 1 – Chemical composition of the duplex and superduplex stainless steel base metals (data from chemical analysis)

DSS

C Si Mn P Cr Cu Ni Mo Ti V Al Nb N Fe Co

0.021[0.020]

0.46 1.48 0.03722.55[22.5]

0.125.64[5.8]

3.13[3.1]

0.013 0.064 0.06 0.04 [0.17] Bal. 0.04

WRC Creq = 25.7, Nieq = 6.4, Predicted FN: 92~64 % ferrite.

SDSS

0.025[<0.030]

0.30 0.86 0.03724.33[25]

0.186.65[6.5]

3.72[3.6]

0.003 0.077 - 0.060.28[0.26]

Bal. 0.05

WRC Creq = 28.1, Nieq = 13.2, Predicted FN: 65~45.5 % ferrite.Values in brackets are obtained from the steel producer.

Table 2 – Welding parameters of plasma arc and fi bre laser welds of DSS and SDSS

Welding process Welding position Preparation ProtectionWelding speed

[mm/min]Plasma arc PA (fl at) 1pass ][ Ar 200

Fibre Laser PA (fl at) 1pass ][ Ar 1 270

a) DSS PAW b) SDSS PAW c) DSS laser d) SDSS laser

Figure 1 – Macrographs of the joints from plasma arc welds and laser welds



51


a) DSS PAW BM b) DSS PAW WM c) DSS PAW WM + HAZ

d) SDSS PAW BM e) SDSS PAW WM f) SDSS PAW WM + HAZ

Figure 2 – Micrographs of the joints from plasma arc welds

Figure 3 – Micrographs of the joints from laser welds

a) DSS laser WM b) DSS laser WM + HAZ

c) SDSS laser WM d) SDSS laser WM + HAZ


52


for plasma welds, in Figure 2, relatively a narrow HAZ and some grain growth affecting subsequent epitaxial growth of the columnar ferrite grains inside the fusion pool, can be seen similar to the study by Urena et al. [29]. Austenite dendrites with the characteristic Widmanstatten structure growing from ferritic grain boundaries were observed in accordance with literature [7, 19, 28, 29, 38-40].

The welds produced by the laser parameters featured a narrow and regular weld metal zone. The as-welded metal structure was made up of elongated ferrite grains with limited amount of austenite, mainly located at grain boundaries, the narrow HAZ was observed for both mate-rial combinations in the laser welds. The base metals, Figures 2 a), 2 d), have shown an elongated grain struc-ture, typical of a rolled product with almost equal amounts of ferrite and austenite in accordance with the literature [1, 16, 31, 33].

3.2 Impact toughness

The mean notch impact values expressed in J are shown in Figure 4, including data from DSS PAW, SDSS PAW, DSS laser and SDSS laser welded joints.

Impact toughness of DSS welds is specifi ed at design temperature or another specifi ed temperature. Although the acceptance criteria vary signifi cantly, examples of typical impact toughness requirements are mentioned to be a minimum of 34 J at -40 °C, and 35 J average and

Duplex stainless steels in general solidify as δ-ferrite, and the austenite phase forms by nucleation at ferrite grain boundaries during cooling to room temperature. Consequently, the amount of austenite resulting at room temperature in welded joints becomes a function of the thermal history experienced during welding. The higher the cooling rate, the higher the ferrite content occurs in the duplex structure [31].

Since the primary solidifi cation phase is ferrite in DSSs, and given the fairly rapid cooling related with a weld ther-mal cycle, diffusional transformation to austenite can be suppressed on cooling to room temperature providing a predominantly ferritic structure at the fusion zone. So, less austenite would be formed if compared with base metal. In particular, the fusion zone (FZ) and the heat-affected zone (HAZ) are generally characterized by an unbalanced ratio between ferrite and austenite because of the high temperatures reached and the high cooling rates which characterize the welding process especially in the joining of thin sections in autogenous mode. As a result, transformation of the austenite and/or homogeni-zation of the ferrite may be incomplete compared to the phase diagram. The microstructure of a fusion weld of the DSS can signifi cantly differ from its BM compared to the martensitic and austenitic types. The HAZ is heated to temperatures close to the solidus, inducing transforma-tion from the original two phase microstructure to ferrite and this retains again on cooling. Here, for plasma arc welds, a signifi cant fusion line was not observed. Mainly

Figure 4 – Notch impact toughness graphs of PA and laser welds of DSS and SDS

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of the WM of approximately 22-60 % may be required [3], but usually 30-70 % range is still acceptable for practi-cal applications [13, 29, 14, 30]. Due to the requirements above mentioned, measured ferrite content of WM val-ues varied between 47 and 74 % for all welds, is within the acceptable range for practical applications. However, in particular laser welds of the duplex grade are recom-mended not to be exposed to corrosion environment under these recommendations. The austenite ferrite ratio of the base metals, Table 3, has dramatically changed with laser welding process and up to 74 ferrite % was mea-sured in the weld metal of the laser welds in accordance with the literature [40].

If the ferrite content measurements and impact toughness data at subzero temperatures are investigated together to determine the ferrite content and impact toughness rela-tionship for the related welds, Figure 5, it could basicly be said that when the ferrite/austenite phase balance is protected after welding, such as close to 50:50, tough-ness values increase in accordance with the literature [31]. When balance changes such as 35:65, or 30:70 as observed in laser welds, subzero temperature toughness values of the weld zones decrease generally with regard to the BM –i.e. decrease from about 120 J to 60 J at -20 °C impact toughness test temperature.

The ferrite/austenite ratio depends on the energy input in welding, since it controls the cooling rate and ferrite/aus-tenite transformation. Studies revealing the determination of the cooling rate of stainless steels including duplex grades and its effects on the properties, also analytical thermal models of stainless steel laser welds are available in the literature [18, 40-42].

Energy input and cooling time are referred to have strong effects on toughness, such that the ferrite content and microhardness decreases with the increasing of cool-ing time. On the other hand, such conditions also tend to produce coarse-grained weld deposits and possibly pre-cipitation of brittle intermetallic phases. Then it is desir-able to control welding conditions such that cooling is slow enough for adequate austenite formation, but fast enough to prevent deleterious precipitation [4, 6, 13, 17, 19, 29, 39 ,40]. Here, in particular for the laser welds, cooling was so fast that adequate austenite could not be formed, that is why up to 74 % ferrite was measured on the weld zones. Since the cooling time is proportional to the amount of heat input, more ferrite is expected when lower heat input is used [19]. Confi rming this situation, ferrite content measurements revealed that more ferrite is measured on laser welds. And this difference between the ferrite and austenite phases content is such that the change in the phase balance for the related joint has led impact toughness values to decrease compared to those of plasma arc welds. Zambon and Bonolli point out that the cooling rate of DSS is roughly twice that of austenitic stainless steels, so, to restore the austenite ferrite phase ratio in the weld metal, additional post-weld heat treat-ment would be required [40].

27 J minimum at -46 °C [11]. Depending on these crite-ria, it can easily be concluded that all joints (except the duplex stainless steel laser weld at the weld metal notch position) pass the minimum requirements. The ductility of both HAZ and weld metal continuously decreased with decreasing temperature in general. The fragments still showed partly ductile fracture surfaces. Plasma arc welds exhibited much higher values compared to laser welds. In particular at -60 °C, laser weld of duplex grade has given values of about only 5 J.

At the weld metal notch positions, plasma arc welds (being within the recommended heat input range) pro-vided quiet good toughness results on the order of 98 J and 106 J, while laser welds resulting only around 5 J and 30 J respectively for DSS and SDSS grades at −60 °C test temperature. When the test temperature increases to −20 °C, values increased up to 120 J for plasma arc welds. For the laser weld fusion zones of both grades, at −20 °C, the toughness results increased up to 60 J.

3.3 Ferrite content

WRC-1992 diagram allows ferrite prediction based on composition up to 100 FN [1]. Taking this into account, Creq and Nieq values of BMs were calculated to predict the ferrite content of the WM, Table 1. Since, a rough conversation from FN to volume percent for the duplex alloys is 70 % [1], due to the diagram, 92 FN so 64 % for duplex and 65 FN so 45.5. % ferrite content are predicted due to the WRC diagram, respectively, for the weld metals of duplex and superduplex grades. It should be noted that the effect of the heat input is not con-sidered in WRC diagram, however it might be helpful in predicting the phases before ferrite content measure-ments. Ferrite content of the welds were obtained with a Fischer Ferritscope on the macrosections across the BM, HAZ and WM. Ferrite % data also include the values obtained from the face, middle, and root parts. Data are given in Table 3. Ferrite content analysis of the welds by image analysis system gave similar values confi rming ferritescope measurements.

In order to maintain the original chemical and physical properties of the as-received duplex BM, the phase bal-ance of the WM and the HAZ is critical [13]. WM shall fulfi ll a Ferrite Number (FN) requirement of FN = 30-70 (approx. 22-70 %) in TIG weldments. With other pro-cesses and at locations exposed to the corrosive environ-ment and/or possible hydrogen cracking, ferrite content

Table 3 – Ferrite content range of the joints

Weld TypeFerrite % due to the position

BM HAZ WM

DSS PAW 48-56 50-60 53-63

SDSS PAW 37-41 45-50 47-54

DSS laser 47-52Too narrow for measurement

62-74

SDSS laser 45-48 57-61


54


98 J and 106 J compared to laser welds resulting only around 5 J and 30 J respectively for DSS and SDSS grades at −60 °C test temperature.

2. Ferrite content measurements to determine the phase variations between phases in WM revealed that the fer-rite content varied in general in an acceptable range which affects the microstructure and so the toughness properties. If good toughness properties are desired, then the phase balance of the weld metal should be kept close to 50:50 % ferrite- austenite ratio, by con-trolling the heat input and cooling rate carefully.

3. Hardness measurements revealed mainly an increase for the weld zones of laser welds up to about 345 HV1 similar to the cases in the literature. Plasma arc welds exhibited relatively more uniform hardness compared to laser welds.

4. Plasma arc welds showed that improved weldability of duplex stainless steel grades leading to higher welding speeds and productivity in welding could be provided with controlled heat input range and acceptable fer-rite/austenite balance. Taking into account the results obtained by fi bre laser welding of these grades, it has become more evident that using proper fi ller metal, the use of hybrid laser system or a short time post-weld treatment would promote more austenite formation that would increase the impact toughness.

3.4 Hardness

Hardness measurements are illustrated in Figure 6.

Maximum weld metal hardness ranged from 316 HV1 to 345 HV1 - the former from DSS PAW and the latter was obtained from DSS laser welds. The hardness generally increased in the weld metal and was highest in the centre, Figure 6. The main feature in the laser welded material was the increased hardness compared to the plasma arc welds in accordance with the literature and this is ascribed to the presence of high amount of ferrite [20, 31, 34].

4 Conclusions

The following conclusions concerning the plasma arc and fi bre laser welds of EN 1.4462 duplex and EN 1.4410 superduplex stainless steel have been drawn:

1. The impact test results showed that all welds have exhibited good toughness properties at low tempera-tures such as down to −60 °C, except for laser welds of the duplex grade, in particular for weld metal notch position. At the WM notch positions, plasma arc welds within the recommended heat input range provided improved impact toughness results on the order of

Figure 5 – Relation between ferrite content and toughness of PA and laser welds

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[4] Karlsson L., Rigdal S., Bergquist E.L. and Arcini, H.: Effects of alloying elements on properties of duplex weld metals. Int. Conf. Duplex 2007, Italy, October 2007, paper 11.

[5] Folkhard E.: Welding metallurgy of stainless steels, Springer-Verlag: Vienna, New York, 1984, p. 186.

[6] Kaluc E. and Taban E.: Paslanmaz Celikler, Gelistirilen Yeni Turleri ve Kaynak Edilebilirlikleri, Stainless steels, their modifi ed types and weldability, TMMOB MMO 2007/461, A publication of Mechanical Engineering Chamber of Turkey, ISBN: 978-9944-89-438-8, 2007 (in Turkish).

[7] Nelson D.E., Baeslack W.A. and Lippold J.C.: Characterization of the weld structure in a duplex stainless steel using color metallography, Materials Characterization, 1997, vol. 39, no. 2-5, pp. 467-477.

[8] NN, Practical guidelines for the fabrication of duplex stainless steels, International Molybdenum Association, UK, 2009.

[9] Charles J.: Composition and properties of duplex stainless steels, Welding of Welding steels, Welding in the World, June 1995, vol.36, pp. 43-54.

Acknowledgements

The authors would like to thank colleagues at ArcelorMittal Belgium, Teknokon, Inc., General Electric R&D Center, Gedik Welding Inc., Metkon Inc., Cimtas Steel Construction Inc., for their technical support. In addition, Dr. L. Karlsson is acknowledged for the valuable suggestions and techni-cal support.

References

[1] Lippold J.C. and Kotecki D.J.: Welding metallurgy and weldability of stainless steels, John Wiley & Sons, New Jersey, 2005, pp. 230-253.

[2] Davis J.R.: ASM Speciality Handbooks: Stainless Steels, American Society for Metals Materials Park, ASM, Ohio, 1994.

[3] Van Nassau L., Meelker H. and Hilkes J.: Welding duplex and superduplex stainless steels, Doc. IIW-1165, Welding in the World, 1993, vol. 31, no. 5, pp. 322-343.

Figure 6 – HV1 graphs

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[21] Karlsson L. and Tolling J.: Experiences and new possibilities in welding duplex stainless steels. Proc., IIW Regional Congress on Welding and Related Inspection Technologies, South Africa, 2006.

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57

About the authorsDr. Emel TABAN ([email protected]) is with Kocaeli University, Engineering Faculty, Dept. of Mechanical Engineering, Kocaeli (Turkey) and Prof. Dr. Erdinc KALUC ([email protected]) is with Kocaeli University, Welding Technology Research Center- KATAEM, Kocaeli (Turkey).


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Welding behaviour of DUPLEX and SUPERDUPLEX …akademikpersonel.kocaeli.edu.tr/emelt/sci/emelt22.05.2013_05.04.06... · 50 Welding behaviour of DUPLEX and SUPERDUPLEX STAINLESS STEELS